Method and apparatus for transmitting and receiving data and feedback in wireless communication system

ABSTRACT

A method of performing communication by a terminal in a wireless communication system includes storing feedback information for data transmitted from a base station in at least one hybrid automatic repeat request (HARQ) process; receiving control information including an indication of feedback triggering; and transmitting the stored feedback information based on the indication of the feedback triggering.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. § 119to Korean Patent Application No. 10-2018-0133896, filed on Nov. 2, 2018,in the Korean Intellectual Property Office, the disclosure of which isincorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates generally to a wireless communication system, andmore particularly, to a method and apparatus for transmitting andreceiving data and feedback in a wireless communication system.

2. Description of the Related Art

To meet the increasing demand for wireless data traffic due to thecommercialization of 4^(th)-generation (4G) communication systems,efforts have been made to develop improved 5^(th)-generation (5G)communication systems or pre-5G communication systems. For this reason,5G communication systems or pre-5G communication systems are alsoreferred to as beyond-4G-network communication systems or post-long termevolution (LTE) systems. For higher data rates, the implementation of 5Gcommunication systems on ultra-high frequency bands (mmWave), e.g., 60GHz, is being considered. In 5G communication systems, beamformingtechnologies, massive multi-input multi-output (MIMO) technologies, fulldimensional MIMO (FD-MIMO) technologies, array antenna technologies,analog beamforming technologies, and large-scale antenna technologieshave been discussed to alleviate propagation path loss and increasingpropagation distances in ultra-high frequency bands.

For system network improvement, in 5G communication systems,technologies such as evolved small cell, advanced small cell, cloudradio access network (RAN), ultra-dense network, device to device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, coordinated multi-points (CoMPs), and interferencecancellation have been developed. In a 5G system, advanced codingmodulation (ACM) schemes including hybrid frequency-shift keying (FSK),frequency quadrature amplitude modulation (QAM) (FQAM), sliding windowsuperposition coding (SWSC), and advanced access schemes (includingfilter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA),and sparse code multiple access (SCMA)) have been developed.

The Internet is now evolving into the Internet of things (IoT), wheredistributed entities, such as objects, exchange and process information.The Internet of everything (IoE) has also emerged, which is acombination of IoT technology and big data processing technology byemploying a connection with a cloud server. In order to implement theIoT, technological elements, such as sensing technology, wired/wirelesscommunication and network infrastructure, service interface technology,and security technology, are required. In this regard, technologies suchas sensor networks, machine to machine (M2M) communication, andmachine-type communication (MTC), have recently been researched forconnection between things. Such an IoT environment may provideintelligent Internet technology (IT) services that create new value tohuman life by collecting and analyzing data generated among connectedthings. IoT may be applied to a variety of fields including smart homes,smart buildings, smart cities, smart or connected cars, smart grids,health care, smart appliances, and advanced medical services, byconverging and combining existing information technology and variousindustries.

Thus, various attempts have been made to apply 5G communication systemsto IoT networks. For example, 5G communication, such as sensor networks,M2M, and MTC, has been implemented by schemes such as beamforming, MIMO,and array antenna. The application of cloud RAN as a big data processingtechnology may also be an example of the convergence of 5G technologyand IoT technology.

As one of many techniques for satisfying the gradually increasing demandfor large-volume communication, a scheme to provide multiple connectionshas been proposed. For example, a carrier aggregation (CA) scheme of anLTE system may provide multiple connections through multiplesub-carriers. Thus, a user may be provided with a service by using moreresources. In addition, through an LTE system, various services such asbroadcast services like multimedia broadcast multicast services (MBMS)may be provided.

SUMMARY

The present disclosure has been made to address the above-mentionedproblems and disadvantages, and to provide at least the advantagesdescribed below.

According to an aspect of the present disclosure, a method of performingcommunication by a terminal in a wireless communication system includesstoring feedback information for data transmitted from a base station(BS) in at least one hybrid automatic repeat request (HARQ) process;receiving control information including an indication of feedbacktriggering; and transmitting the stored feedback information, based onthe indication of the feedback triggering.

According to another aspect of the present disclosure, a method ofperforming communication by a BS in a wireless communication systemincludes transmitting a first set of data to a terminal; transmitting,to the terminal, control information including an indication of feedbacktriggering; and receiving feedback information for a second set of datain at least one HARQ process based on the indication of the feedbacktriggering, the second set of data being among the first set oftransmitted data.

According to another aspect of the present disclosure, a terminal forperforming communication in a wireless communication system includes atleast one buffer; a transceiver; and a processor coupled with thetransceiver and the at least one buffer, and configured to store, in theat least one buffer, feedback information for data transmitted from a BSin at least one HARQ process; control the transceiver to receive controlinformation including an indication of feedback triggering; and controlthe transceiver to transmit the stored feedback information, based onthe indication of the feedback triggering.

According to another aspect of the present disclosure, a based station(BS) for performing communication in a wireless communication systemincludes a transceiver; and a processor coupled with the transceiver andconfigured to control the transceiver to transmit a first set of data toa terminal; transmit, to the terminal, control information including anindication of feedback triggering; and receive feedback information fora second set of data in at least one HARQ process based on theindication of the feedback triggering, the second set of data beingamong the first set of transmitted data.

According to another aspect of the present disclosure, a non-transitorycomputer-readable recording medium having recorded thereon a program forexecuting, on a computer, the method of performing communication by theterminal in the wireless communication system is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates a basic structure of a time-frequency domain that isa radio resource domain in which data or a control channel istransmitted in a downlink (DL) or an uplink (UL) in a new radio (NR)system, according to an embodiment;

FIG. 2 illustrates a state where data for services considered in a5th-generation (5G) or NR system, such as enhanced mobile broadband(eMBB), ultra-reliable and low-latency communications (URLLC), ormassive machine type communications (mMTC), is assigned infrequency-time resources, according to an embodiment;

FIG. 3 illustrates a state where data for services considered in a 5G orNR system, such as eMBB, URLLC, or mMTC, is assigned in frequency-timeresources, according to an embodiment;

FIG. 4 illustrates a process in which one transport block is dividedinto several code blocks and a cyclic redundant check (CRC) is added,according to an embodiment;

FIG. 5 illustrates a state in which synchronization signals and aphysical broadcast channel (PBCH) are mapped in frequency and timedomains in a 3rd-generation partnership project (3GPP) NR system;

FIG. 6 is a diagram describing symbols in which one synchronizationsignal (SS)/PBCH block is mapped in a slot, according to an embodiment;

FIG. 7 is a diagram describing symbols among symbols within 1 ms inwhich an SS/PBCH block is transmittable, according to an embodiment;

FIG. 8 is a diagram describing a slot and symbols among slots andsymbols within 5 ms in which an SS/PBCH block is transmittable,according to an embodiment;

FIG. 9 is a diagram describing a method of transmitting data andtransmitting HARQ-acknowledgement (ACK) feedback informationcorresponding to the data in an LTE or NR system, according to anembodiment;

FIG. 10 is a diagram describing a method, performed by a user equipment(UE), of feeding back HARQ-ACK information about data currentlyprocessed by a UE in a HARQ process, by transmitting control informationwithout transmitting data, according to an embodiment;

FIG. 11 is a diagram describing a structure of a UE for receiving andprocessing DL data, according to an embodiment;

FIG. 12 is a diagram describing a structure of a UE for receiving andprocessing DL data, according to an embodiment;

FIG. 13 is a diagram describing a method, performed by a UE, of reducinga HARQ processing time for feeding back HARQ-ACK, according to anembodiment;

FIG. 14 is a flowchart illustrating a HARQ-ACK feedback operation of aUE, according to an embodiment;

FIG. 15 is a diagram describing a data rate in initial transmission andretransmission, according to an embodiment;

FIG. 16 is a diagram describing a HARQ feedback processing method of aUE, according to an embodiment;

FIG. 17 is a diagram describing a method, performed by a UE, of storingan information bit in a buffer based on a code block (CB) decodingsuccess or failure, according to an embodiment;

FIG. 18 is a block diagram of a UE, according to an embodiment; and

FIG. 19 is a block diagram of a BS, according to an embodiment.

DETAILED DESCRIPTION

The disclosure relates to a wireless communication system, and providesa method and apparatus for transmitting feedback within a limited timeby enabling fast data processing when a UE receives data and transmitsfeedback.

New 5G communication, an NR access technology, has been designed toallow various services to be freely multiplexed in time and frequencyresources, and thus waveform/numerology and a reference signal may bedynamically or freely allocated according to the need of a service. Toprovide an optimal service to a UE in wireless communication, optimizeddata transmission based on measurement of channel quality andinterference quantity is needed, making accurate channel statemeasurement indispensable.

However, unlike 4G communication in which channel and interferencecharacteristics do not vary greatly with frequency resources, a 5Gchannel has channel and interference characteristics that change largelywith a service, requiring a support for a subset at a frequency resourcegroup (FRG) level to allow separate measurements. In the NR system, atype of a supportable service may be categorized into eMBB, mMTC, andURLLC. The eMBB may be regarded as high-speed transmission ofhigh-volume data, mMTC may be regarded as minimization of power of theUE and accesses by multiple UEs, and URLLC may be regarded as a serviceaiming at high reliability and low latency. Depending on a type of aservice applied to the UE, different requirements may be applied.

Along with the recent on-going research into next-generationcommunication systems, various schemes for scheduling communication withthe UE have been discussed. Thus, there is a need for efficientscheduling and data transmission/reception schemes that considercharacteristics of the next-generation communication systems.

As such, in a communication system, a plurality of services may beprovided to a user. A method of providing each of the plurality ofservices in the same time period based on the characteristics and anapparatus capable of using the method may be required.

When the embodiments of the disclosure are described, technical mattersthat are well known in a technical field of the disclosure and are notdirectly related to the disclosure will not be described. By omittingunnecessary description, the subject matter of the disclosure can bemore clearly described without being obscured.

Some elements described herein will be exaggerated, omitted, orsimplified in the attached drawings. The size of each element does notentirely reflect the actual size of the element. In each drawing, anidentical or corresponding element will be referred to as an identicalreference numeral. A controller may also be referred to as a processor.

Throughout the specification, a layer (or a layer apparatus) may also bereferred to as an entity. In other embodiments of the disclosure, theentity may be a hardware apparatus in the form of a chip.

Throughout the disclosure, the expression “at least one of a, b or c”indicates only a, only b, only c, both a and b, both a and c, both b andc, all of a, b, and c, or variations thereof.

Blocks of a flowchart and a combination of flowcharts may be representedand executed by computer program instructions. The computer programinstructions may be stored in a general-purpose computer, aspecial-purpose computer, or a processor of other programmable dataprocessing devices, such that the instructions implemented by thecomputer or the processor of the programmable data processing deviceproduce a means for performing functions specified in the flowchartand/or block diagram block or blocks. The computer program instructionsmay also be stored in a computer usable or computer-readable memory thatmay direct a computer or other programmable data processing apparatus tofunction in a particular manner, such that the instructions stored inthe computer usable or computer-readable memory produce an article ofmanufacture including instructions that implement the function specifiedin the flowchart and/or block diagram block or blocks. The computerprogram instructions may also be loaded onto a computer or otherprogrammable data processing apparatus to cause a series of operationalsteps to be performed on the computer or other programmable apparatus toproduce a computer implemented process, such that the instructions thatexecute the computer or other programmable apparatus may provide stepsfor implementing the functions specified in the flowchart and/or blockdiagram block or blocks.

In addition, each block represents a module, segment, or portion ofcode, which includes one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat in other implementations, the function(s) noted in the blocks mayoccur out of the order indicated. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently or theblocks may sometimes be executed in the reverse order, depending on thefunctionality involved.

In the current embodiment, the term “unit”, as used herein, denotes asoftware or hardware component, such as a field programmable gate array(FPGA) or application specific integrated circuit (ASIC), which performscertain tasks. However, the meaning of “unit” is not limited to softwareor hardware. “Unit” may advantageously be configured to reside on theaddressable storage medium and configured to reproduce one or moreprocessors. Thus, a unit may include, by way of example, components,such as software components, object-oriented software components, classcomponents and task components, processes, functions, attributes,procedures, subroutines, segments of program code, drivers, firmware,microcode, circuitry, data, databases, data structures, tables, arrays,and variables. The functionality provided in the components and “units”may be combined into fewer components and “units” or further separatedinto additional components and “units”. In addition, components and“units” may be implemented to execute one or more computer processingunits (CPUs) in a device or a secure multimedia card. In the embodimentsof the disclosure, a “unit” may include one or more processors.

A wireless communication system has evolved from an initial one thatprovides a voice-oriented service to a broadband wireless communicationsystem that provides a high-speed and high-quality packet data service,such as 3GPP high speed packet access (HSPA), LTE or evolved universalterrestrial radio access (E-UTRA), LTE-Advanced (LTE-A or E-UTRAEvolution), 3GPP2 high rate packet data (HRPD), ultra mobile broadband(UMB), and the Institute of Electrical and Electronics Engineers (IEEE)802.16e. As a 5G wireless communication system, 5G or NR communicationstandards have been established.

A 5G or NR system as a representative example of a broadband wirelesscommunication system adopts orthogonal frequency division multiplexing(OFDM) in a DL and a UL. More specifically, cyclic-prefix (CP) OFDM isadopted in a DL, and discrete Fourier transform spreading (DFT-S) OFDMand CP-OFDM are adopted in a UL. The UL is a radio link through which aUE transmits data or a control signal to a BS (i.e., a gNodeB), and theDL is a radio link through which the BS transmits data or a controlsignal to the UE. The above-described multiple access scheme separatesdata or control information for each user by allocating and operatingtime-frequency resources on which the data or the control information iscarried for each user, so that the time-frequency resources do notoverlap each other, that is, so that orthogonality is realized.

The 5G or NR system employs a HARQ scheme that retransmits data in aphysical layer when decryption fails in initial transmission of thedata. HARQ refers to a scheme in which when a receiver fails toaccurately decrypt (decode) data, the receiver transmits informationindicating a decoding failure, i.e., a negative acknowledgement (NACK),to a transmitter to allow the transmitter to retransmit the data in thephysical layer. The receiver improves data reception performance bycombining the data retransmitted by the transmitter with data that failsto be decoded previously. When accurately decoding the data, thereceiver transmits information indicating a decoding success, i.e., anACK, to the transmitter to allow the transmitter to transmit new data.

FIG. 1 illustrates a basic structure of a time-frequency domain that isa radio resource domain in which data or a control channel istransmitted in a +DL or a UL in an NR system, according to anembodiment.

In FIG. 1, a horizontal axis represents a time domain and a verticalaxis represents a frequency domain. A minimum transmission unit in thetime domain may be an OFDM symbol, in which N_(symb) OFDM symbols 1-02may be gathered to constitute one slot 1-06. The length of the subframemay be defined as 1.0 millisecond (ms), and the length of a radio frame1-14 may be defined as 10 ms. A minimum transmission unit in thefrequency domain may be a subcarrier, and the transmission bandwidth ofthe whole system may include N_(RB) ^(DL) or N_(RB) ^(UL) subcarriers1-04 in total.

In the time-frequency domain, a basic unit of a resource may be aresource element (RE) 1-12, and may be indicated as an OFDM symbol indexand a subcarrier index. A resource block (RB) 1-08 or a physicalresource block (PRB) may be defined as N_(symb) successive OFDM symbols1-02 in the time domain or N_(RB) successive subcarriers 1-10 in thefrequency domain. Accordingly, one RB 1-08 may be composed ofN_(symb)×N_(RB) REs 1-12. In general, a minimum transmission unit ofdata may be the RB unit. In the NR system, generally, N_(symb)=14,N_(RB)=12, and N_(BW) and N_(RB) may be proportional to a bandwidth of asystem transmission band. The data rate may be increased in proportionto the number of RBs scheduled for the UE.

In the NR system, for a frequency division duplexing (FDD) system inwhich the DL and the UL are discriminated by frequencies and operated,the DL transmission bandwidth and the UL transmission bandwidth maydiffer from each other. The channel bandwidth indicates an RF bandwidththat corresponds to a system transmission bandwidth. Table 1 indicates acorresponding relationship between the system transmission bandwidthdefined in the LTE system that is 4G wireless communication prior to theNR system, and the channel bandwidth. For example, the LTE system havinga channel bandwidth of 10 megahertz (MHz) may have a transmissionbandwidth composed of 50 RBs.

TABLE 1 Channel bandwidth BW_(channel) [MHz] 1.4 3 5 10 15 20Transmission bandwidth 6 15 25 50 75 100 configuration N_(RB)

The NR system may support a bandwidth that is broader than the channelbandwidth of LTE provided in Table 1.

In the NR system, scheduling information regarding DL data or UL datamay be delivered from the BS to the UE through downlink controlinformation (DCI). The DCI may be defined according to various formats.That is, the DCI may be scheduling information (UL grant) regarding ULdata, scheduling information (DL grant) regarding DL data, or compactDCI having small-size control information. Additionally, the DCI mayapply spatial multiplexing using multiple antennas, and may be powercontrol. For example, DCI format 1-1, which is scheduling controlinformation (DL grant) regarding DL data, may include at least one ofthe following pieces of control information:

Carrier Indicator: indicates a frequency carrier in which a signal istransmitted;

DCI Format Indicator: indicates whether a DCI is for a DL or a UL;

Bandwidth Part (BWP) Indicator: indicates a BWP in which a signal istransmitted;

Frequency Domain Resource Assignment: indicates an RB of a frequencydomain allocated for data transmission. A resource to be expressed maybe determined based on a system bandwidth and a resource assignmentscheme;

Time Domain Resource Assignment: indicates an OFDM symbol of a slot inwhich a data-related channel is to be transmitted;

VRB-to-PRB Mapping: indicates a scheme for mapping a virtual RB (VRB)index with a physical RB (PRB) index;

Modulation and Coding Scheme (MCS): indicates a modulation scheme and acoding rate used for data transmission. That is, this may indicateinformation about whether a modulation scheme is quadrature phase shiftkeying (QPSK), 16 QAM, 64QAM, or 256QAM, and a coding rate valueindicating a transport block size (TBS) and channel coding information;

Code block Group (CBG) transmission information: indicates informationabout a CBG to be transmitted when CBG retransmission is set;

HARQ Process Number: indicates a process number of HARQ;

New Data Indicator: indicates whether transmission is HARQ initialtransmission or retransmission;

Redundancy version: indicates a redundancy version of HARQ; and

Transmit Power Control (TPC) command for Physical Uplink Control Channel(PUCCH): indicates a TPC command for a PUCCH that is a UL controlchannel.

For the aforementioned PUSCH transmission, time domain resourceassignment may be delivered through information regarding a slot inwhich the PUSCH is to be transmitted. A start symbol position S may beincluded in the slot, and a symbol number L may represent the number ofsymbols to which the PUSCH is mapped. In the aforementioneddescriptions, S may be a relative position from the start of the slot, Lmay be the number of consecutive OFDM symbols, and S and L may bedetermined from a start and length indicator value (SLIV) defined asEquation (1) below.

if (L−1)≤7 then

SLIV=14·(L−1)+S

else

SLIV=14·(14−L+1)+(14−1−S)

where 0<L≤14−S  (1)

In the NR system, for the UE, a table including an SLIV value, a PUSCHmapping type, and information about a slot in which a PUSCH is to betransmitted in one row may be generally configured through RRCconfiguration. In the following time domain resource assignment of theDCI, by indicating an index value of the above-described configuredtable, the BS may deliver an SLIV value, a PUSCH mapping type, andinformation about a slot in which a PUSCH is to be transmitted to theUE.

In the NR system, the PUSCH mapping type may be defined as a type A anda type B. In the PUSCH mapping type A, a first symbol among demodulationreference signal (DMRS) symbols may be located in a second or third OFDMsymbol of the slot. In the PUSCH mapping type B, the first symbol amongthe DMRS symbols may be located in a first OFDM symbol of a time domainresource assigned for PUSCH transmission.

The DCI may be transmitted on a physical downlink control channel (PDCCHor control information, hereinafter used interchangeably) throughchannel coding and modulation.

Generally, the DCI may be scrambled with a particular radio networktemporary identifier (RNTI) or a terminal identifier, independently foreach terminal, and a CRC is added to the DCI which is then channel-codedand independently configured as a PDCCH for transmission. The PDCCH maybe transmitted after the PDCCH is mapped in a control resource setCORESET configured in the UE.

The DL data may be transmitted on a PDSCH that is a physical channel forDL data transmission. The PDSCH may be transmitted after a controlchannel transmission period, and scheduling information such as adetailed mapping position and a modulation scheme in the frequencydomain may be determined based on the DCI transmitted through the PDCCH.

Using the MCS among the control information of the DCI, the BS maynotify the UE of a modulation scheme applied to the PDSCH to betransmitted and a size of data to be transmitted (a transport block size(TBS)). The MCS may be composed of a predetermined number of bits (i.e.,5 bits or more/less). The TBS may correspond to the size before achannel coding for error correction is applied to the data, that is, atransport block (TB), which the BS intends to transmit.

The TB may include a medium access control (MAC) header, a MAC CE, oneor more MAC service data units (SDUs), and padding bits. The TB mayindicate the unit of data transmitted down to the physical layer fromthe MAC layer, or a MAC protocol data unit (PDU).

A modulation scheme supported in the NR system may be QPSK, 16QAM,64QAM, and 256QAM, and respective modulation orders Qm may correspond to2, 4, 6, and 8. For QPSK modulation, 2 bits per symbol may betransmitted, and for 16QAM, 4 bits per symbol may be transmitted.Further, 6 bits per symbol may be transmitted for 64QAM, and 8 bits persymbol may be transmitted for 256QAM.

FIG. 2 illustrates a state where data for services considered in a 5G orNR system, such as eMBB, URLLC, and mMTC, is assigned in frequency-timeresources, according to an embodiment. FIG. 3 also illustrates a statewhere data for services considered in a 5G or NR system, such as eMBB,URLLC, and mMTC, is assigned in frequency-time resources, according toan embodiment.

Referring to FIGS. 2 and 3, a scheme may be seen in which frequency andtime resources are assigned for information transmission in each system.

In FIG. 2, data for eMBB, URLLC, and mMTC is assigned in a total systemfrequency band 2-00. When URLLC data 2-03, 2-05, and 2-07 are generatedand need to be transmitted during assignment and transmission of eMBBdata 2-01 and mMTC data 2-09 in a particular frequency band, parts withwhich the eMBB data 2-01 and the mMTC data 2-09 are already assigned maybe emptied or transmission may not occur, such that the URLLC data 2-03,2-05, and 2-07 may be transmitted. The URLLC data 2-03, 2-05, and 2-07may be assigned to a part of a resource assigned with the eMBB data 2-01and transmitted because a delay time of the URLLC data among theaforementioned services needs to be reduced. When the URLLC data isadditionally assigned to the eMBB-assigned resource and transmitted,eMBB data may not be transmitted in the redundant frequency-timeresources, such that transmission performance for the eMBB data may bedegraded. That is, in this case, an eMBB data transmission failure dueto the URLLC assignment may occur.

In FIG. 3, a total system frequency band 3-00 may be divided intosub-bands 3-02, 3-04, and 3-06. A service and data may be transmitted ineach divided sub-band 3-02, 3-04, and 3-06. Sub-bandconfiguration-related information may be previously determined, and thesub-band configuration-related information may be transmitted from a BSto a UE through high-layer signaling.

Sub-band-related information may be arbitrarily divided by the BS or anetwork node, such that services may be provided to the UE withoutseparate transmission of sub-band configuration-related information tothe UE. FIG. 3 shows a state in which a sub-band 3-02 is used fortransmission of eMBB data 3-08, a sub-band 3-04 is used for transmissionof URLLC data 3-10, 3-12, and 3-14, and a sub-band 3-06 is used fortransmission of mMTC data 3-16.

A length of a transmission time interval (TTI) used for transmission maybe shorter than a length of a TTI used for eMBB mMTC transmission. Aresponse to information related to URLLC may be transmitted faster thana case with eMBB or mMTC, such that for URLLC, information may betransmitted and received with low latency.

A structure of a physical channel used for each type to transmit theforegoing three types of services or data may differ. For example, atleast one of a length of a TTI, an assignment unit of a frequencyresource, a structure of a control channel, or a mapping method of datamay be different.

While three types of services and data have been described above, moretypes of services and corresponding data may exist, and the disclosureis applicable to more types of services and corresponding data.

The present disclosure may be applied to a wireless communication systemrather than the NR system.

FIG. 4 illustrates a process in which one transport block is dividedinto several code blocks and a CRC is added, according to an embodiment.

Referring to FIG. 4, a CRC 4-03 may be added to an end part or startpart of a TB 4-01 to be transmitted in a UL or DL. The CRC may have 16or 24 bits or a pre-fixed bit number, or may have a bit number variablewith a channel condition, and may be used to determine a channel codingsuccess. The TB 4-01 and the CRC-added part may be divided into severalCBs 4-07, 4-09, 4-11, and 4-13. The group of CBs are indicated by 4-05.A maximum size for the CB may be previously defined, and in this case,the last CB 4-13 may be smaller in size than the other CBs or may bepadded with 0, a random value, or 1 to have the same length as the otherCBs. To each of the CBs 4-07, 4-09, 4-11, and 4-13, CRCs 4-17, 4-19,4-21, and 4-23 may be added, as indicated by 4-15. The CRC may have 16or 24 bits or a pre-fixed bit number, and may be used to determine achannel coding success.

The TB 4-01 and a cyclic generator polynomial may be used to generatethe CRC 4-03, and the cyclic generator polynomial may be defined invarious manners. For example, assuming that a cyclic generatorpolynomial for a 24-bit CRC isg_(CRC24A)(D)=D²⁴+D²³+D¹⁸+D¹⁷+D¹⁴+D¹¹+D¹⁰+D⁷+D⁶++D⁵+D⁴+D³+D+1

and L=24, then for TB data a₀, a₁, a₂, a₃, . . . , a_(A−1), the CRC p₀,p₁, p₂, p₃, . . . , p_(L-1) may be determined to be a value having aremainder of 0 after dividing a₀D^(A+23)+a₁ D^(A+22)+ . . .+_(A−1)D²⁴+p₀D²³+p₁D²²+ . . . +p₂₂D¹+p₂₃ by g_(CRC24A)(D).

Meanwhile, the above description has been made by taking a CRC length Lof 24 as an example, but this is merely an example. The CRC length L maybe determined to be various lengths such as 12, 16, 24, 32, 40, 48, or64. After the CRC is added to the TB in the foregoing manner, they maybe divided into N CBs 4-07, 4-09, 4-11, and 4-13. The CRCs 4-17, 4-19,4-21, and 4-23 may be added to each of the CBs 4-07, 4-09, 4-11, and4-13, as indicated by 4-15. To generate the CRC added to the CB, a CRChaving a length that is different from or a cyclic generator polynomialthat is different from one used to generate the CRC is added to the TB.However, the CRC 4-03 added to the TB 4-01 and the CRCs 4-17, 4-19,4-21, and 4-23 added to the CBs 4-07, 4-09, 4-11, and 4-13 may beomitted according to a type of a channel code to be applied to acorresponding CB. For example, when a low-density parity check (LDPC)code, instead of a turbo code, is applied to a CB, the CRCs 4-17, 4-19,4-21, and 4-23 to be inserted to the respective CBs 4-07, 4-09, 4-11,and 4-13 may be omitted. However, even when LDPC is applied, the CRCs4-17, 4-19, 4-21, and 4-23 may be added to the respective CBs 4-07,4-09, 4-11, and 4-13. In addition, when a polar code is used, a CRC maybe added or omitted.

As illustrated in FIG. 4, a maximum length of a CB may be determinedaccording to a type of channel coding to be applied, and a TB to betransmitted and a CRC added to the TB may be divided into CBs based onthe maximum length of the CB. In an existing LTE system, a CB-specificCRC is added to a CB, and data bits of the CB and the CRC are encodedinto a channel code to determine coded bits, in which for the respectivecoded bits, a previously agreed-upon rate-matching bit number isdetermined.

The BS is an entity that performs resource assignment of the terminal,and may be at least one of a gNode B (gNB), an eNode B (eNB), a Node B,a wireless access unit, a BS controller, or a node on a network. Theterminal may include UE, a mobile station (MS), a cellular phone, asmartphone, a computer, or a multimedia system capable of performingcommunication functions.

A DL may be a wireless transmission path of a signal for transmissionfrom the BS to the UE, and a UL may mean a wireless transmission path ofa signal for transmission from the UE to the BS. While embodiments ofthe disclosure are described by using an NR system as an example, thedisclosure may also be applied to other communication systems having asimilar technical background or channel form. Also, the disclosure mayalso be applied to other communication systems through somemodifications within a range that does not largely depart from the scopeof the disclosure based on the knowledge of one of ordinary skill in theart.

Conventional physical channels and signals may be used interchangeablywith data or control signals. For example, a physical downlink sharedchannel (PDSCH) is a physical channel for transmitting data, but in thedisclosure, a PDSCH may be used as data.

High-layer signaling is a method of delivering a signal from a BS to aUE by using a DL data channel of a physical layer or from the UE to theBS by using a UL data channel of the physical layer, and may bementioned as RRC signaling or a MAC CE.

In current LTE and NR, the UE may attempt decoding for TB reception in aphysical layer. When any one TB succeeds in decoding, the UE may deliveran ACK to an upper layer thereof; when the TB fails in decoding, the UEmay deliver a NACK to the upper layer thereof. To transmit ACK or NACKinformation back to a transmission end, the UE may deliver ACK/NACKinformation from the upper layer to a physical layer to form feedbackinformation and a signal.

The UE may include a reception apparatus operating with hardware and areception apparatus operating with software. The UE may store receptiondata and a decoding result, i.e., ACK/NACK information in a softwareentity. When the UE transmits ACK/NACK information as feedback, the UEmay prepare for transmission by retrieving ACK/NACK information storedin the software entity to a hardware entity, during which muchprocessing time is consumed.

Thus, the disclosure provides a method and apparatus in which the UEstores an ACK/NACK in the hardware entity and feeds back the same.Meanwhile, when the UE attempts TB decoding in DL data transmission, theUE may determine transmission success and failure by performing decodingfor each CB. When the UE fails in decoding with respect to one CB or TB,the UE may store a log likelihood ratio (LLR) value for performingdecoding or similar information in a soft buffer. When a correspondingTB is retransmitted, the stored LLR value may be combined withretransmitted data for use in decoding. In such implementation, when thedata for retransmission of the TB is received, the data needs to becombined with the LLR value stored in the soft buffer and decoding withrespect to all CBs needs to be performed again. That is, even for a CBsucceeding in initial transmission, decoding has to be newly performed.This lengthens a processing time in retransmission. Therefore, thedisclosure provides a method and apparatus in which information bits ofa succeeding CB are stored to prevent a processing time from increasingeven in retransmission.

FIG. 5 illustrates a state in which synchronization signals and a PBCHare mapped in frequency and time domains in a 3GPP NR system, accordingto an embodiment. A primary synchronization signal (PSS) 5-01, asecondary synchronization signal (SSS) 5-03, and a PBCH 5-05 are mappedto four OFDM symbols, in which the PSS 5-01 and the SSS 5-03 are mappedto twelve RBs and the PBCH 5-05 is mapped to twenty RBs. FIG. 5 shows atable providing information for how a frequency band of twenty RBschanges according to subcarrier spacing (SCS). A resource region inwhich the PSS, the SSS, and the PBCH are transmitted may be referred toas an SS/PBCH block.

FIG. 6 is a diagram describing symbols in which one SS/PBCH block ismapped in a slot, according to an embodiment.

When comparing an LTE system using SS of 15 kilohertz (kHz) with an NRsystem using SS of 30 kHz, SS/PBCH blocks 6-11, 6-13, 6-15, and 6-17 ofthe NR system may be transmitted at positions 6-01, 6-03, 6-05, and 6-07at which cell-specific reference signals (CRSs) transmitted at all timesin the LTE system may be avoided. This is intended to allow co-existenceof the LTE system and the NR system in one frequency band.

FIG. 7 is a diagram describing symbols within 1 ms in which an SS/PBCHblock is transmittable, with respect to SS, according to an embodiment.FIG. 8 is a diagram describing a slot and symbols among slots andsymbols within 5 ms in which an SS/PBCH block is transmittable, withrespect to SS, according to an embodiment. In a region where an SS/PBCHblock is transmittable, the SS/PBCH block does not need to betransmitted at all times, and the SS/PBCH block may be transmitted ormay not be transmitted according to selection of a BS.

Reception data and a decoding result, i.e., HARQ-ACK information, may bestored in a hardware entity and the stored HARQ-ACK information may befed back.

FIG. 9 is a diagram describing a method of transmitting data andtransmitting HARQ-ACK feedback information corresponding to the data inan LTE or NR system, according to an embodiment.

Referring to FIG. 9, data 9-01, 9-03, and 9-05 corresponding to HARQprocesses 1, 2, and 3 may be respectively transmitted, and HARQ-ACKinformation 9-11, 9-13, and 9-15 corresponding to the respective data9-01, 9-03, and 9-05 may be fed back. A minimum processing time fortransmitting corresponding HARQ-ACK information after receiving data bythe UE is fixed, such that the UE has to feed back the HARQ-ACKinformation as fast as a corresponding minimum processing time.

FIG. 10 is a diagram describing a method, performed by a UE, of feedingback HARQ-ACK information about data currently processed by a UE in aHARQ process, simply by transmitting control information withouttransmitting data, according to an embodiment.

Referring to FIG. 10, the BS may transmit to the UE, control informationindicating that HARQ-ACK information regarding data needs to be fed backor a TB being processed in a current HARQ process needs to be fed back10-01.

The UE having received the control information may feed back theHARQ-ACK information regarding data being kept or processed in currentHARQ processes to the BS 10-03. For example, when 16 HARQ processes areconfigured for the UE for DL data transmission, the UE may feed back16-bit or 32-bit HARQ-ACK information to the BS based on aconfiguration.

FIG. 11 is a diagram describing a structure of a UE for receiving andprocessing DL data, according to an embodiment.

Referring to FIG. 11, the UE may roughly include a hardware entity 11-01and a software entity 11-03. Division into the hardware entity 11-01 andthe software entity 11-03 may be made by different blocks or differentimplementations. The UE may perform signal reception and processing inthe hardware entity 11-01, store HARQ-ACK feedback information that isreception success or failure information after performing processing,and deliver the stored feedback information to an upper layer.Thereafter, in an operation where the UE feeds back the HARQ-ACKinformation, the UE may read the HARQ-ACK information stored in thesoftware entity into the hardware entity, and generate and transmit a ULsignal based on the HARQ-ACK information. Meanwhile, a time for the UEto read the HARQ-ACK information stored in the software entity into thehardware entity is required, increasing a delay time.

To solve the aforementioned delay issue, the operation of the embodimentpresented in FIG. 12 will be described.

FIG. 12 is a diagram describing a structure of a UE for receiving andprocessing DL data, according to an embodiment.

Referring to FIG. 12, a receiving UE includes not only a HARQ-ACKstorage space of a software entity 12-03 for delivering HARQ-ACKinformation that is a decoding result with respect to reception data toan upper layer of the UE, but also a buffer 12-05 for storing theHARQ-ACK information in a hardware entity 12-01. The buffer 12-05 forstoring the HARQ-ACK information in the hardware entity 12-01 may storeHARQ-ACK information that is a decoding result with respect to datacorresponding to each HARQ process.

FIG. 13 is a diagram describing a method, performed by a UE, of reducinga HARQ processing time for feeding back a HARQ-ACK, according to anembodiment.

As an example, when the UE receives an instruction for HARQ-ACKtransmission for HARQ processes from the BS, the UE may transmit, usinga UL control channel, the HARQ-ACK information that is stored in thebuffer of the hardware entity to feed back the HARQ-ACK information. Asillustrated in FIG. 13, the UE does not perform an operation of readingHARQ-ACK information stored in the software entity for HARQ-ACKtransmission into the hardware entity, thereby reducing a HARQprocessing time for feeding back the HARQ-ACK information.

Descriptions will be made of an ACK/NACK transmission method for allHARQ processes of the UE through a BS configuration.

The receiving UE may store all HARQ processes or HARQ-ACK informationfor configured HARQ-ACK processes in the buffer 12-05 of the hardwareentity 12-01. Thereafter, the UE may prepare for transmission of a ULcontrol channel for transmission of all stored HARQ-ACK information. Forexample, HARQ-ACK information for HARQ process numbers 1 through 16 maybe stored using a bit map, and a HARQ process number that has not beentransmitted or is blank may be set to a default value (NACK or ACK). TheUE may prepare for transmission of HARQ-ACK information for all HARQprocesses or a configured HARQ process at all times through a UL controlchannel, and newly update the HARQ-ACK information based on a decodingresult with respect to reception data. Meanwhile, the BS may indicateHARQ-ACK information transmission for all HARQ process numbers stored inthe UE by transmitting downlink control information (DCI) including aHARQ-ACK transmission indicator of 1 bit for all the HARQ processnumbers, and the UE may transmit HARQ-ACK information for all the HARQprocess numbers by using a prepared UL control channel.

FIG. 14 is a flowchart illustrating a HARQ-ACK feedback operation of aUE, according to an embodiment.

Referring to FIG. 14, the UE performs DL data reception and decoding andstores HARQ-ACK information in a buffer of a hardware entity in step 1.In step 2, the UE updates HARQ-ACK information corresponding to a HARQprocess number to a bit map, and prepares for transmission of a ULcontrol channel. When the UE receives a HARQ-ACK transmission indicatorfor all HARQ process numbers from the BS in step 3, the UE transmits aUL control channel including HARQ-ACK information regarding all the HARQprocess numbers in step 4.

When the UE does not receive the indicator from the BS, the UE mayreceive subsequent DL data and then perform a corresponding operationagain. The foregoing operations may be performed each time when data isreceived, to update HARQ-ACK transmission preparation.

When UL transmission is made from the UE to the BS through an unlicensedband, the UE may perform a channel access procedure or listen-beforetalk (LBT). The UE may access the unlicensed band when the unlicensedband is determined to be in an idle state as a result of performing thechannel access procedure, and perform configured signal transmission. Asystem and device for transmitting and receiving a signal by using theunlicensed band has limited channel access, such that HARQ-ACKtransmission for all the HARQ process numbers may be used. When theforegoing disclosure is applied to the UE using the unlicensed band, anoperation of reading HARQ-ACK information from the software entity intothe hardware entity may not be performed, thus reducing an HARQprocessing time.

A method will be described in which the UE stores information bits of aCB succeeding in decoding an initial transmission and does not performdecoding for a retransmission.

FIG. 15 is a diagram for describing a data rate in initial transmissionand retransmission, according to an embodiment.

An NR system supports partial retransmission in the unit of a CB group,and considering this point, as illustrated in FIG. 15, an average orinstant data rate in initial transmission and retransmission may becalculated by dividing a sum of bit numbers included in CBs actuallytransmitted or a sum of CB sizes by a transmission length. Morespecifically, as indicated by 15-01, in initial transmission, data istransmitted in a terabyte (TB) size of Di during a slot of Ti, such thatan average data rate may be calculated as Di/Ti. However, as indicatedby 15-03, in retransmission, partial retransmission may be performed fora CB failing in initial transmission, such that a sum of CBs to betransmitted may have a size of Dr (=Di) and for a transmission time Tr(=Ti), an average data rate may be calculated as Dr/Tr. Herein, the sumof sizes of CBs actually transmitted in a retransmission, Dr (=Di), andthe transmission time Tr (=Ti) may be reduced compared to an initialtransmission. For example, a slot of 14 symbols may be required totransmit X CBs in an initial transmission, but a slot of two symbols maybe required to transmit Y (=X) CBs in a retransmission. Thus, whenalready succeeding CBs (i.e., successfully transmitted CBs) have to bedecoded even though a small Dr and Tr are required for retransmission aspartial retransmission of CBs, or when the UE uses an existingimplementation, it is difficult to shorten a processing time.

FIG. 16 is a diagram describing a HARQ feedback processing method of aUE, according to an embodiment.

Referring to FIG. 16, an existing implementation method is indicated bya solid line and an implementation method proposed in the disclosure isexpressed by a dotted line. In step 16-01, when the UE attempts TBdecoding for a received signal, the UE determines transmission successor failure while performing decoding for each CB. When the UE fails indecoding with respect to one CB or TB, the UE stores an LLR value forperforming decoding or similar information in a soft buffer, in step16-02. When a corresponding TB is retransmitted, the stored LLR valuemay be combined with retransmitted data for use in decoding. In such animplementation, when the data for retransmission of the TB is received,the data needs to be combined with the LLR value stored in the softbuffer and decoding with respect to all CBs needs to be performed again.That is, even for a CB succeeding in initial transmission, decoding hasto be newly performed.

As described above, a slot of 14 symbols may be required to transmit XCBs using a TB size of Di in initial transmission, but a slot of twosymbols may be required to transmit Y (=X) CBs in retransmission.However, in retransmission, the UE has to perform decoding again for XCBs when processing Y (=X) CBs, such that the UE may store HARQ-ACKinformation in step 16-04 and the same time is needed to prepare forcorresponding HARQ-ACK feedback transmission as in initial transmissionin step 16-05. Thus, the disclosure provides a method and apparatus forpreventing a retransmission processing time from increasing like in thecase of initial transmission.

For example, a first method includes storing an information bit for a CBand a CRC bit succeeding in decoding.

Additionally or alternatively, a second method includes storing aninformation bit for a CB succeeding in decoding, without CRC.

The information bit for the CB succeeding in decoding may mean a hardinformation bit of 0 or 1 determined after decoding of soft information,i.e., an LLR value. A method proposed in the disclosure is indicated bya solid line in FIG. 16. More specifically, when the UE storesinformation about a CB succeeding in decoding in a hard buffer as instep 16-03 of FIG. 16, the UE does not need to additionally decode a CBsucceeding in initial transmission, in a retransmission stage.

Meanwhile, the term “hard buffer” in step 16-03 may be replaced withanother term. As in the foregoing example, a slot of 14 symbols may berequired to transmit X CBs using a TB size of Di in initialtransmission, but a slot of two symbols may be required to transmit Y(=X) CBs in retransmission. The UE according to the disclosure mayperform decoding with respect to Y CBs in combination with an LLR valuestored in a soft buffer during retransmission, and may not performadditional decoding with respect to (X-Y) CBs because decodinginformation for (X-Y) CBs is stored in the hard buffer. Thus, the UE maystore HARQ-ACK information in step 16-04, and a time required forpreparation for PUCCH transmission for the HARQ-ACK information in step16-05 may be reduced when compared to initial transmission.

FIG. 17 is a diagram describing a method, performed by a UE, of storingan information bit in a buffer based on a CB decoding success orfailure, according to an embodiment.

The storage space of a buffer may be minimized according to the methodillustrated in FIG. 17. In the method, the UE may receive a TB andperform decoding for each CB, such that contents stored in the buffermay be determined according to whether transmission succeeds or fails.During decoding for each CB, an LLR value or similar information isstored in the soft buffer in step 17-01 for use in decoding during thenext transmission for a CB failing in decoding. On the other hand,during decoding for each CB, the UE stores a decoding information bit inthe hard buffer (as in the above-described first and second method) fora CB succeeding in decoding in step 17-02 to prevent decoding from beingperformed additionally during the next transmission.

A transmitter, a receiver, and a processor of each of the UE and the BSare illustrated in FIGS. 18 and 19. Transmission and reception methodsof the BS and the UE are illustrated to perform the data decoding methodand the HARQ-ACK feedback storage and transmission method in theabove-described embodiments.

FIG. 18 is a block diagram of a UE, according to an embodiment.

As illustrated in FIG. 18, a UE includes a UE receiver 18-00, a UEtransmitter 18-04, and a UE processor 18-02. The UE receiver 18-00 andthe UE transmitter 18-04 are collectively referred to as a transceiver.The transceiver may transmit and receive a signal to and from the BS.The signal may include control information and data.

The transceiver may include an RF transmitter that up-converts andamplifies a frequency of a transmission signal and an RF signal thatlow-noise-amplifies a received signal and down-converts a frequency. Thetransceiver may receive a signal through a radio channel and output thereceived signal to the UE processor 18-02, and transmit a signal outputfrom the UE processor 18-02 through the radio channel.

The UE processor 18-02 may control a series of processes such that theUE operates according to the above-described embodiment of thedisclosure. For example, the UE processor 18-02 may control the UEreceiver 18-00 to receive data and control information from the BS, anddetermine to process a TB included in the data based on the controlinformation and store and transmit HARQ-ACK. Thereafter, the UEtransmitter 18-04 may deliver feedback of the data to the BS.

FIG. 19 is a block diagram of a BS, according to an embodiment.

As illustrated in FIG. 19, a BS includes a BS receiver 19-01, a BStransmitter 19-05, and a BS processor 19-03. The BS receiver 19-01 andthe BS transmitter 19-05 will be collectively referred to as atransceiver. The transceiver may transmit and receive a signal to andfrom the UE. The signal may include control information and data. Tothis end, the transceiver may include an RF transmitter that up-convertsand amplifies a frequency of a transmission signal and an RF signal thatlow-noise-amplifies a received signal and down-converts a frequency. Thetransceiver may receive a signal through a radio channel and output thereceived signal to the BS processor 19-03, and transmit a signal outputfrom the BS processor 19-03 through the radio channel.

The BS processor 19-03 may control a series of processes such that theBS operates according to the above-described embodiment of thedisclosure. For example, the BS processor 19-03 may control transmissionof a HARQ-ACK feedback. Thereafter, the BS transmitter 19-05 maytransmit control information for transmitting a HARQ-ACK transmitted inthe above-described method, and the BS receiver 19-01 may receivefeedback with respect to the transmitted data from UEs.

According to the disclosure, a processing time in data reception may beshortened, and a feedback preparation time may also be reduced.

The embodiments of the disclosure may be practiced in combination andthe disclosure may also be carried out in an LTE system or a 5G system.

While the present disclosure has been particularly shown and describedwith reference to certain embodiments thereof, it will be understood bythose of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the disclosure as defined by the appended claims and theirequivalents

What is claimed is:
 1. A method of performing communication by aterminal in a wireless communication system, the method comprising:storing feedback information for data transmitted from a base station inat least one hybrid automatic repeat request (HARQ) process; receivingcontrol information including an indication of feedback triggering; andtransmitting the stored feedback information based on the indication ofthe feedback triggering.
 2. The method of claim 1, wherein the feedbackinformation is stored in a hard buffer from among a plurality of buffersincluding the hard buffer and a soft buffer.
 3. The method of claim 1,further comprising storing at least one code block (CB) that wassuccessfully decoded among the data transmitted from the base station.4. The method of claim 1, further comprising storing at least one codeblock (CB) that was successfully decoded and storing a cyclic redundantcheck (CRC) of the at least one CB, the at least one CB being among thedata transmitted from the base station.
 5. The method of claim 3,wherein storing the feedback information comprises storingidentification information for the at least one CB that was successfullydecoded in a hard buffer and storing identification information for atleast one CB that was not successfully decoded in a soft buffer.
 6. Amethod of performing communication by a base station in a wirelesscommunication system, the method comprising: transmitting data to aterminal; transmitting, to the terminal, control information includingan indication of feedback triggering; and receiving feedback informationfor data in at least one hybrid automatic repeat request (HARQ) processbased on the indication of the feedback triggering, the data being amongthe transmitted data.
 7. The method of claim 6, wherein the feedbackinformation is stored in a hard buffer from among a plurality of buffersof the terminal, the plurality of buffers including the hard buffer anda soft buffer.
 8. A terminal for performing communication in a wirelesscommunication system, the terminal comprising: at least one buffer; atransceiver; and a processor coupled with the transceiver and the atleast one buffer, and configured to: store, in the at least one buffer,feedback information for data transmitted from a base station in atleast one hybrid automatic repeat request (HARQ) process; control thetransceiver to receive control information including an indication offeedback triggering; and control the transceiver to transmit the storedfeedback information based on the indication of the feedback triggering.9. The terminal of claim 8, wherein the feedback information is storedin a hard buffer from among a plurality of buffers including the hardbuffer and a soft buffer.
 10. The terminal of claim 8, wherein theprocessor is further configured to store at least one code block (CB)that was successfully decoded among the data transmitted from the basestation.
 11. The terminal of claim 8, wherein the processor is furtherconfigured to store at least one code block (CB) that was successfullydecoded and store a cyclic redundant check (CRC) of the at least one CB,the at least one CB being among the data transmitted from the basestation.
 12. The terminal of claim 10, wherein the processor is furtherconfigured to store identification information for the at least one CBthat was successfully decoded in a hard buffer and identificationinformation for at least one CB that was not successfully decoded in asoft buffer.
 13. A base station for performing communication in awireless communication system, the base station comprising: atransceiver; and a processor coupled with the transceiver and configuredto control the transceiver to: transmit data to a terminal; transmit, tothe terminal, control information including an indication of feedbacktriggering; and receive feedback information for data in at least onehybrid automatic repeat request (HARQ) process based on the indicationof the feedback triggering, the data being among the transmitted data.14. The base station of claim 13, wherein the feedback information isstored in a hard buffer from among a plurality of buffers of theterminal, the plurality of buffers including the hard buffer and a softbuffer.
 15. A non-transitory computer-readable recording medium havingrecorded thereon a program for executing the method of claim 1 on acomputer.